The present invention relates to a valve stem seal assembly, and in particular to a seal for a valve stem seal assembly found in overhead valve internal combustion engines.
Those skilled in the art will appreciate the manner in which intake and exhaust valves are employed in cylinder heads of internal combustion engines. In conventional overhead valve internal combustion engines, a pair of valves reciprocates in timed alternation to provide intermittent communication between the intake and exhaust manifolds and a combustion chamber. As is well known, the intake port of a combustion chamber is opened and closed by the reciprocating motion of at least one intake valve. The intake valve permits fuel mixed with air to flow into the combustion chamber. In addition, an internal combustion engine has at least one exhaust valve and associated exhaust port for releasing expended combustion gases into the atmosphere. Lubrication is provided to the upper portions of the valves. Because temperatures in the combustion chamber may approach or exceed 1000 degrees Centigrade, any lubricating oil exposed to these temperatures will vaporize or burn leaving behind deposits that may interfere with the proper sealing of the valves and cause rapid deterioration. Valve stem seal assemblies are used to seal against leakage of oil between each valve guide and its associated valve stem.
It is therefore necessary to provide seals around the upper region of the valve stems and along the valve guide down to the manifolds and combustion chamber. A typical valve stem seal takes the form of a cylinder partially closed at one end by the valve seal. The cylindrical region seats about the valve guide to maintain the valve seal stationary. An upper region of the valve stem is surrounded by the valve seal when the valve stem is fully inserted into the valve seal assembly.
Conventional valve seal assemblies comprise individual body and seal components that typically must be assembled into the valve seal assembly. Such multiple components and associated assembly increases the cost of the valve seal assembly. In some engines, unitary elastomeric valve stem seals are fitted over or atop each valve guide, wherein the seal component is frictionally mounted directly to the guide. Traditional manufacture of such seals has been only on a unitary batch basis, or via one batch at a time. Thus, although much progress has been achieved in the art of valve stem design and construction, cost-effective techniques for enhancement of strength of materials, along with streamlined manufacturing techniques remain areas in need of additional improvement.
The inventor of the present invention has recognized these and other problems associated with valve stem seals. To this end, the inventor has developed a valve stem seal assembly comprising of a retainer, including a cavity, a cylindrical passageway, an annular flange and having one or more built-in sprues, and a jacket having an upper region at one end, an annular seal at the opposite end and an intermediate region therebetween. The jacket is bonded to the retainer.
In another embodiment of the invention, a valve stem seal assembly comprises a retainer, including a cavity, a cylindrical passageway, an annular flange and having one or more built-in sprues, ajacket, and a gap. The gap is defined by a bottom of the cavity, a surface of the cylindrical passageway and a top surface of a valve guide to accommodate variances in valve guide height.
A manufacturing method is presented for manufacturing a valve stem seal assembly. The retainer is placed upon a tool plate that contains a circumferential groove. Elastomeric material is poured into the built-in sprues of the retainer, filling the circumferential groove on the tool plate, the built-in sprues and the cavity of the retainer. As the circumferential groove is filled with elastomeric material, the annular seal is formed. The jacket is formed as the elastomeric material fills the built-in sprues and the cavity. Finally, the elastomeric material is cured and the jacket is integrally bonded with the retainer.